1. Field of the Invention
The present invention relates to a fuel gas generating apparatus for a fuel cell comprising a reformer that reforms a hydrocarbon fuel into a hydrogen rich gas, and in particular to a fuel gas generating apparatus for a fuel cell having superior start-up characteristics.
2. Description of the Related Art
A conventional technology is known (for example, Japanese Unexamined Patent Application, First Publication, No. 2000-154002 and Japanese Unexamined Patent Application, First Publication, No. 2000-53403) wherein a hydrocarbon fuel such as methanol or methane is reformed into a hydrogen rich fuel gas by a fuel gas generating apparatus comprising a reformer, this fuel gas and an oxidizing gas (for example, air) are supplied to a fuel cell, and electrical generation is carried out.
This fuel gas generating apparatus comprises a vaporizer that generates a fuel vapor by vaporizing a raw liquid fuel that is a mixture of a raw fuel such as methanol and water, an autothermal reformer (below, abbreviated “reformer”) that generates a hydrogen rich reformed gas from a partially oxidized raw fuel gas by adding a reforming air to the fuel vapor generated by the vaporizer, a heat exchanger that lowers the temperature of the reformed gas generated by the reformer, a CO eliminator that eliminates the carbon monoxide in the reformed gas by adding CO eliminating air to the reformed gas whose temperature has been lowered by the heat exchanger and generates a fuel gas, and a fuel cell that generates electricity by an electrochemical reaction between the fuel gas supplied to an anode electrode and the air (oxidizing gas) supplied to the cathode electrode.
In this fuel gas generating apparatus, the system as a whole must be warmed up until the gas composition of the fuel gas after start-up stabilizes and the fuel gas temperature stabilizes at a temperature that allows supplying the fuel gas to the fuel cell.
In the conventional warm-up method, for example, a start-up burner is installed in the reformer, a heater is provided on the reformer, a heat medium (for example, air) that has been heated by the heater is allowed to flow to the heat exchanger and the CO eliminator. First, cooling water for the heat exchanger and cooling water for catalytic temperature adjustment of the CO eliminator are warmed up by supplying external heat using these heat sources, the catalyst in the reformer and the catalyst in the CO eliminator are warmed up to a temperature equal to or greater than the active temperature, the system is warmed up to a temperature equal to or greater than the fuel gas dew point temperature, and at the same time, the vaporizer is warmed up. After the warm-up of the vaporizer has completed, both the fuel vapor generated in the vaporizer and the reforming air are supplied to the reformer in the amount supplied during the idling operation after warm-up is completed, the reforming reaction is started, the warm-up is carried out starting from the reformer, which is in the front end, and the warm-up progresses gradually towards the back end.
However, in this warm-up method, a long time passes until the catalyst of the CO eliminator in the back end reaches the activation temperature, and in addition, a long time passes in warming up the cooling water for temperature adjustment of the catalyst in the CO eliminator and the internal system path, and as a result the warm-up of the system as a whole may require tens of minutes, and subsequently several minutes are required for the composition of the fuel gas to stabilize.
In the case of being employed in an industrial field requiring a fast start-up, and in particular, in fuel cell vehicles, in order to make driving possible until the composition of the fuel gas stabilizes, a large-capacity storage battery must be installed, and thus there is the problem that the system becomes large.
Thus, it is an object of the present invention to provide a fuel gas generating apparatus for a fuel cell that makes possible the fast warm-up of the reformer, CO eliminator, system gas path, and the like, and makes possible the fast stabilization of the fuel gas composition.